The following tables are a guide for establishing shaft and bearing fits for miniature and instrument bearings when the expansion coefficients of the shaft and housing are similar or when the operating temperature differential between them is nominal. In other conditions, modification in fits and internal clearance may be required.

Radial Clearance Range

Operating
Conditions

Load

Speed

Shaft Diameter

Average Fit

Fit Range

Radial Load

Thrust Load
Springs

Rotating Shaft

Light

Low

B- 0.0002
B- 0.0004

0.0002L

0
0.0004L

K25

K36 TO K58

Light
Medium

High
Low to High

B- 0.0001
B- 0.0003

0.0001L

0.0001T
0.0003L

K36

K36 TO K58

Heavy

High

B- 0.0000
B- 0.0002

Line to Line

0.0002T
0.0002L

K36

K58

Stationary Shaft

Normal

Low to High

B- 0.0002
B- 0.0004

0.0002L

0
0.0004L

See Rotating Housing

B = Nominal Bearing Bore

L = Loose Fit

T = Tight Fit

Radial Clearance Range

Operating
Conditions

Load

Speed

Housing Diameter

Average Fit

Average Fit

Fit Range

Fit Range

Radial Load

Thrust Load
Springs

Rotating Housing

Light

Low to High

D-0.0001

D- 0.0000

D-0.0003

D- 0.0002

0.00005T

Line to Line

0.0002L
0.0003T

0.0002L
0.0002T

K36

K58

Medium to Heavy

Low to high

D- 0.0002
D- 0.0004

D- 0.0001
D- 0.0003

0.00015T

0.0001T

0.0001L
0.0004T

0.0001L
0.0003T

K36

K58

Stationary Housing

Light to Heavy

Low to High

D +/-0.0002
D- 0.0000

0.00025L

0.0002L

0
0.0005L

0
0.0004L

See Rotating Shaft

D = Nominal Bearing OD

L = Loose Fit

T = Tight Fit

Light Load

C/P < 25

Low Speed

> 5000 RPM

Medium Load

C/P 15-25

High Speed

> 1500 RPM
(Bearings w/OD <= 3/8")

Heavy Load

C/P > 15

High Speed

> 3000 RPM (Bearings w/OD > 3/8")

C = Dynamic Road Rating

P = Radial Equivalent Load

* For closer running accuracy or reduced axial play K13 internal clearance may be used provided that the fit of the outer ring is line to line or looser

** For closer running accuracy or reduced axial play K25 internal clearance may be used provided that the fit of the outer ring in the housing is line to line or looser.

Re: Bearing Pocket Dimensions

01/28/2017 11:27 PM

All of my first programs solved formulas from the 18th edition of the MH bible. The last one (for that machine) solved for the volume of an ellipsoid given three perpendicular axises relative to the the major and minor dimensions of the ellipsoid.

I wrote it in assembly language to fit nicely into the 2k of memory the machine had in 1977. I was 13!

I have that edition on my Christmas list. The one I used was my dad's and nobody knows where it went.

Re: Bearing Pocket Dimensions

Don't use the Machinery's Handbook for fits and tolerances, use the bearing manufacturers, you can get this information from the bearing manufacturer, SKF for example.

Now if your on a project,.. school, personal or for work. You'll need to know and understand the type of fits from the bearing manufacturer that you require, at first look, its a little difficult to read but you get adjusted after awhile.